U.S. patent application Ser. No. 09/774,852, filed on even date herewith, is directed to coverage for the sheet placement control of the apparatus described herein. Similarly, U.S. Pat. No. 6,311,971, filed Jul. 6, 2000, is directed to the curl control mechanism.
This invention relates to the accumulation of sheets exiting a printer into a neat stack and then binding the sheets, as by stapling. Apparatus to achieve such function is commonly known as a finisher.
The handling of paper and other sheets to reliably produce neat stacks which can be bound as neat stacks entails problems arising from the characteristics of such sheets to buckle and to move from the forces stored by the disturbed sheet. Consequently, the apparatus to stack and bind sets of sheets can be cumbersome or unreliable.
This invention moves the sheets as they exit a printer by frictional contact made within about two or less inches of a reference surface defining the edge of the stack to be bound. The stack is positioned with the edge of the stack within the binding device. Each sheet in a set first rests on a table and a moving device then moves over the sheet. The moving device contacts the surface of the sheet with sufficient friction to move the sheet laterally, until the sheet contacts a blocking surface, which is a reference surface defining the side of the desired stack. Since the friction member and the reference surface are less than two inches apart in the embodiment disclosed, buckling of the sheets normally does not occur and the sheets do not spring away from the reference surface. To assure reliable blocking contact between the sheet and the reference surface, a curl elimination device is employed effectively at the binding device. To further prevent sheet movement, a positive clamp engages the sheet from above after it reaches the reference surface. In the embodiment disclosed, the moving devices are fingers which are biased toward the reference surface by resilient force selected to be low enough in force so that the finger stops when the sheet contacts the reference surface.
The implementation described has two frictional elements, which move alternately in directions perpendicular to each other toward reference surfaces, which are perpendicular to each other. A single frictional surface moving toward the junction of the two reference surfaces should be entirely effective.